1. Field of the Invention
The invention relates to apparatus for gravity separation of foreign matter of different densities suspended in a flowing liquid.
2. Description of the Prior Art
The API (American Petroleum Institute) separator has been in long use and its operation is based on the principle of gravity differential separation. The fluid is usually a waste water which flows slowly through an elongated settling area. The foreign matter is in part lighter weight free oil in the water which floats upwardly for accumulation on the surface of the water while heavier weight foreign matter such as solids within the water gradually settle out and accumulate on the bottom of the separator. Separation occurs by natural action of gravity on the lighter and heavier foreign matter in the water over a period of time and there is no attempt to enhance or accelerate separation. A major disadvantage of the API separator is its size. The greater the flow volume and the higher the concentration of foreign matter, the greater must be the length of the separator to perform effectively. In recognition of this inherent deficiency, various means have been devised to accelerate separation and thereby allow a decrease in size of the separator.
U.S. Pat. No. 3,810,832 discloses a separator wherein separation is promoted by use of a barrier made of filaments of polypropylene positioned widthwise to the path of flow. The affinity of oils to strips of polypropylene and the like is disclosed in U.S. Pat. No. 3,668,118.
Another means is disclosed in U.S. Pat. No. 3,847,813 where a plurality of corrugated plates are placed transversely in the path of flow of waste water. Solids accumulate in the valleys while oils accumulate within the peaks of the corrugations. The oils and solids are then permitted to flow by gravity upwardly and downwardly as the case may be provided in the peaks and valleys.
A variation of the above-noted devices is incorporated in a curved plate-finger oil-water separator manufactured by Hellevoet B. V. of Holland. Separation of entrapped oil is promoted by mixing air with the waste water and then allowing oil droplets to form on a series of upwardly curved plates positioned laterally relative to the flow path.
Another separator, offered for sale by Atlas Chemical Industries, increases the rate of separation by diverting a flow of waste water in a downwardly inclined direction between a plurality of laterally positioned corrugated plates. Heavy sediment accumulates in the valleys of the corrugations and is carried downward for accumulation at the lower end of the plates. Oils accumulate within the peaks of the corrugations and flow upwardly in a counter-flow direction to the path of the waste water.
U.S. Pat. No. 3,451,555 wherein separation of water from a slurry is achieved by cascading the slurry over an inclined surface formed from transversely spaced bars.